BBS door games were one case of "anything goes" in terms of theme -- anything the author could describe and you could navigate through menu hot-keys was fair game. That said, I've got to say that this particular BBS appears to have a somewhat meagre spread. One thing's for sure -- they weren't selling out by laying out all the popular BBS doors all the other boards had. Star Trek Cryptograms? I suppose every niche has sub-niches.
Now for some bona fide blockbusters: first, a run of Earthworm Jim pics. EJ was the brainchild of Doug Ten Napel, a gifted animator who was responsible for making Virgin's Disney adaptations (Aladdin, the Jungle Book) blockbusters. Then he was brought on board by Playmates to devise a new line of action figures tied to some cross-media franchise: historically these things were cartoons first, then toys, but in this case they bucked the trend and debuted the characters in video games. As his follow-up, he used an enormous amount of clay to make The Neverhood -- a lost classic that's recently become supported by SCUMMVM. I was first introduced to him when his surname was used as a sound effect in an issue of Rob Schrab's comic book Scud the Disposable Assassin.
That's a rendition by iCE's eternal luminary Toon Goon, aka Cyberchrist. The former sobriquet suited him better, mastering the cartoonish visual idiom of thick outlines and large fields of flat colour. That was another iCE pic, this one by Biscuit. iCE remained a home to toony ANSIs after the fad passed from the rest of the scene. This particular rendition of Jim is less exaggerated, with some weird foreshortening in effect as EWJ points a just-out-of-frame ray gun at the viewer. The 80-column limitations of the ANSI medium led to some curious aesthetic constraints, specifically it was odd how there was no upper limit to the length of a piece but its width remained limited to a kind of tall vertical slice. (This was addressed in the .BIN format which could be of arbitrary width -- but it was difficult (read: more or less impossible) to use those in a BBS context. They were just gallery pieces for artpacks. You'll have to take my word for it, since I haven't yet found any video-game themed .BINs to use to illustrate this particular point. Now two EWJ villains, the former piece by Misfit is of Henchrat (I looked it up on the Earthworm Jim wiki... yes, there is an Earthworm Jim wiki) followed by one of Pete Puppy. Gotta say, I wouldn't have pegged these as video game characters if not for being explicitly called out / being pointed to them.